A user of a vehicle smart key may wirelessly operate and control starting of a vehicle, opening and/or closing a vehicle door or trunk, or a welcome function by using a smart key. In particular, the welcome function may be a function enabling a user to approach a vehicle and operate a smart key to control unfolding an outside mirror (an outside mirror in a folded state is automatically spread) or control turning on a puddle lamp positioned at a lower end of the outside mirror or a door handle lamp, or control turning on a tail light or a room lamp to enhance visibility.
The welcome function may not always be in an ON state. That is, in order to avoid battery discharge and increase starting performance, the welcome function may be turned off when a predetermined period of time (for example, fourteen days) has lapsed since an ignition of a vehicle was turned off and the vehicle was parked with doors locked.
Thus, while the smart key controller of the vehicle is operated while the welcome function is maintained in an ON state for the predetermined period of time after parking, the smart key controller may consumes a relatively large amount of dark current by periodically transmitting a wireless signal (for example, a low frequency (LF) signal) for smart key and authentication using battery power, leading to a situation where the welcome function cannot be maintained for a relatively long period of time.